Pump, especially for a fuel injection device for an internal combustion engine

ABSTRACT

A pump having least one pump element with a pump piston guided in a sealed fashion in a cylinder bore ( 26 ) of a housing part delimiting a pump working chamber in the cylinder bore, and driven into a stroke motion. The working chamber is connected to an inlet conduit through by an inlet valve opening into the pump working chamber and to an outlet conduit through an outlet valve opening out from the working chamber. The inlet valve has a valve element acted on in a closing direction by a valve spring. The inlet conduit includes a first blind bore which adjoins the pump working chamber and has a smaller diameter than the cylinder bore a valve seat is formed at the transition from the cylinder bore to the first blind bore, and a second blind bore, as another part of the inlet conduit, feeds into the first blind bore.

PRIOR ART

The invention is based on a pump, in particular for a fuel injectionapparatus for an internal combustion engine, as generically defined bythe preamble to claim 1.

A pump of this kind is known from DE 198 48 035 A1. This pump has atleast one pump element with a pump piston that is guided in a sealedfashion in a cylinder bore of a housing part and delimits a pump workingchamber in the cylinder bore with its end surface. The pump piston isdriven into a stroke motion. The pump working chamber is connected to aninlet conduit via a connection controlled by an inlet valve opening intothe pump working chamber and is connected to an outlet conduit via aconnection controlled by an outlet valve opening out from the pumpworking chamber. The inlet valve has a valve element that cooperateswith a valve seat and a valve spring acts on this valve element in thedirection of the valve seat. The part of the inlet conduit feeding intothe pump working chamber is comprised of a separate component that alsocontains the valve seat; this component is inserted into a bore of thehousing part. The bore of the housing part is closed with a screw plug.The production and assembly of the known pump are complex and costly dueto the large number of individual parts.

ADVANTAGES OF THE INVENTION

The pump according to the invention, with the characterizing features ofclaim 1, has the advantage over the prior art that it is simple andinexpensive to produce and assemble since the number of its individualparts has been reduced.

Advantageous embodiments and modifications of the pump according to theinvention are disclosed in the dependent claims.

DRAWINGS

An exemplary embodiment of the invention is shown in the drawings andwill be explained in detail in the subsequent description.

FIG. 1 shows a longitudinal section through a pump and

FIG. 2 shows an enlarged detail of the pump, which is labeled II in FIG.1.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIGS. 1 and 2 show a pump that is particularly provided for a fuelinjection apparatus for an internal combustion engine, for example of amotor vehicle. The pump delivers fuel at a high pressure of up to 2000bar, for example to an accumulator. The pump has a housing that has, forexample, a housing part 10 and a flange part 11 connected to it. Thehousing has a drive shaft 12 disposed in it, which drives one or morepump elements 14 disposed in the housing. Preferably, a number of pumpelements 14 are disposed distributed around the circumference of thedrive shaft 12. A bearing 16 in the housing part 10 and a bearing 18 inthe flange part 11 support the drive shaft 12 so that it can rotatearound an axis 13; it is driven by the engine in a manner that is notshown. The drive shaft 12 has a cam section 20 that supports a strokering 22. The pump element 14 has a pump piston 24 that is guided so thatit can slide in a sealed fashion in a cylinder bore 26 of the housingpart 10 extending at least approximately radially in relation to thedrive shaft 12. The pump piston 24 is supported with its piston base 25against the stroke ring 22; the piston base 25 is kept in contact withthe stroke ring 22 by a spring 28, which is supported at one end againstthe housing part 10 and at the other end, against the piston base 25.

The end surface of the pump piston 24 delimits a pump working chamber 30in the cylinder bore 26. An inlet valve 32 that opens into the pumpworking chamber 30 can connect the pump working chamber 30 to a fuelinlet conduit 34 in which low pressure prevails. In addition, an outletvalve 36 that opens toward the accumulator can connect the pump workingchamber 30 to the accumulator via a fuel outlet conduit 38 extending inthe housing part 10. When the drive shaft 12 rotates, it drives the pumppiston 24 in a stroke motion by means of the cam section 20 and thestroke ring 22. When the pump piston 24 moves radially inward, itexecutes an intake stroke during which the inlet valve 32 is opened sothat fuel flows into the pump working chamber 30 via the fuel inletconduit 34 while the outlet valve 36 is closed. When the pump piston 24moves radially outward, it executes a delivery stroke during which theinlet valve 32 is closed and the fuel compressed by the pump piston 24flows at high pressure through the open outlet valve 36, the fuel outletconduit 36, and into the accumulator.

In the housing part 12, a first blind bore 42 that constitutes a part ofthe fuel inlet conduit 34 adjoins the pump working chamber 30 disposedin the end region of the cylinder bore 26 oriented radially away fromthe drive shaft 12. The first blind bore 42 has a smaller diameter thanthe cylinder bore 26 and preferably extends at least approximatelycoaxial to the cylinder bore 26. The first blind bore 42 ends inside thehousing part 10. The transition from the cylinder bore 26 to the firstblind bore 42 is embodied, for example, as at least approximatelyconical and constitutes a valve seat 44 for the inlet valve 32. Theinlet valve 32 has a valve element 46, which is embodied, for example,as a ball, and cooperates with the valve seat 44 in order to control theconnection of the pump working chamber 30 to the fuel inlet conduit 34.A prestressed valve spring 48, for example in the form of a helicalcompression spring, acts on the valve element 46 in the direction of thevalve seat 44. A support element in the form of a spring plate can bedisposed between the valve spring 48 and the valve element 46. The valvespring 48 can be supported in stationary fashion either against thehousing part 10 or, as shown in the figure, against the end surface ofthe pump piston 24.

A second blind bore 50, which is let into the housing part 10 and alsoends in the housing part 10, feeds into the first blind bore 42 asanother part of the fuel inlet conduit 34. The second blind bore 50extends inclined in relation to the first blind bore 42, preferably atleast approximately perpendicular to the first blind bore 42 and atleast approximately parallel to the rotation axis 13 of the drive shaft12. The second blind bore 50 is let into the housing part 10 from a sidesurface 52 oriented toward the flange part 11. The fuel inlet conduit 34continues in the flange part 11, starting from a side surface 54 of theflange part 11; the flange part 11 can be provided with a connection 56for an inlet line via which fuel is supplied from a fuel tank, forexample by means of a fuel-supply pump. A sealing element 58 can beclamped in place at the transition of the fuel conduit 34 between theflange part 11 and the housing part 10. The sides surfaces 52 and 54 ofthe housing part 10 and the flange part 11 facing each other extend, forexample, at least approximately perpendicular to the rotation axis 13 ofthe drive shaft 12 and can be embodied as flat. The housing part 10 andthe flange part 11 are attached to each other in a manner that is notshown, for example by means of a number of screws.

The blind bores 42 and 50 that make up the fuel conduit 34 in thehousing part 10 can be simply let into the housing part 10 respectivelyfrom the cylinder bore 26 and from the side surface 52. The housing part10 does not have any openings on its outside for the fuel conduit 34.The only additional components required for the inlet valve 32 are thevalve element 46, the valve spring 48, and the support element possiblyprovided between them. It is possible for a number of pump elements 14to be provided with a single shared housing part 10 that contains acorresponding number of cylinder bores 26 and blind bores 42 and 50.Alternatively, it is also possible for each pump element 14 to beprovided with a separate housing part 10 that contains only one cylinderbore and one pair of blind bores 42, 50. The housing parts 10 of thepump elements 14 are then attached to one another in a suitable fashion.

As part of the fuel outlet conduit 38, a bore 60 that extends at leastapproximately perpendicular to the longitudinal axis of the cylinderbore 26 feeds into the pump working chamber 30 in the cylinder bore 26.The bore 60 is embodied with a multiply stepped diameter, its a endsection with a small diameter feeding into the pump working chamber 30.The end section is adjoined at its end oriented away from the pumpworking chamber 30 by a middle section of the bore 60; the transitionbetween the end section of the and the middle section can be embodied,for example, as approximately conical and constitutes a valve seat 62for the outlet valve 36. A valve element 64 of the outlet valve 36, forexample in the form of a ball, cooperates with the valve seat 62 inorder to control the connection of the pump working chamber 30 to thefuel outlet conduit 38. A screw plug 66 is screwed into an outer sectionof the bore 60 that has a diameter larger than that of the middlesection and is provided with an internal thread. A prestressed valvespring 68, for example in the form of a helical compression spring, isclamped between the screw plug 66 and the valve element 64 and acts onthe valve element 64 in the direction of the valve seat 62.

1-7. (canceled)
 8. A pump for a fuel injection apparatus for an internalcombustion engine, the pump comprising at least one pump element (14)having a pump piston (24) guided in a sealed fashion in a cylinder bore(26) of a housing part (10) which delimits a pump working chamber (30)in the cylinder bore (26), the pump piston (24) being driven into astroke motion, the pump working chamber (30) being connected to an inletconduit (34) via a connection controlled by an inlet valve (28) openinginto the pump working chamber (30) and connected to an outlet conduit(38) via a connection controlled by an outlet valve (36) opening outfrom the pump working chamber (30), the inlet valve (32) having a valveelement (46) that cooperates with a valve seat (44) and being acted onin a closing direction toward the valve seat (44) by a valve spring(48), the inlet conduit (34) in the housing part (10) having a part inthe form of a first blind bore (42), which adjoins the pump workingchamber (30) in the cylinder bore (26) and having a smaller diameterthan the cylinder bore (26), the valve seat (44) being formed at thetransition from the cylinder bore (26) to the first blind bore (42), anda second blind bore (50), as another part of the inlet conduit (34),feeding into the first blind bore (42).
 9. The pump according to claim8, wherein the first blind bore (42) extends at least approximatelycoaxial to the cylinder bore (26).
 10. The pump according to claim 8,wherein the second blind bore (50) extends inclined in relation to thefirst blind bore (42) in the housing part (10).
 11. The pump accordingto claim 9, wherein the second blind bore (50) extends inclined inrelation to the first blind bore (42) in the housing part (10).
 12. Thepump according to claim 10, wherein the second blind bore (50) extendsat least approximately perpendicular to the first blind bore (42). 13.The pump according to claim 11, wherein the second blind bore (50)extends at least approximately perpendicular to the first blind bore(42).
 14. The pump according to claim 8, wherein the second blind bore(50) starts from a side wall (52) of the housing part (10) that adjoinsanother housing part (11).
 15. The pump according to claim 12, whereinthe second blind bore (50) starts from a side wall (52) of the housingpart (10) that adjoins another housing part (11).
 16. The pump accordingto claim 13, wherein the second blind bore (50) starts from a side wall(52) of the housing part (10) that adjoins another housing part (11).17. The pump according to claim 8, wherein the housing part (10)contains a drive shaft (12) supported so that it can rotate in order todrive the at least one pump element (14), wherein the cylinder bore (26)and the first blind bore (42) extend at least approximately radial tothe rotation axis (13) of the drive shaft (12), and wherein the secondblind bore (50) extends at least approximately parallel to the rotationaxis (13) of the drive shaft (12).
 18. The pump according to claim 9,wherein the housing part (10) contains a drive shaft (12) supported sothat it can rotate in order to drive the at least one pump element (14),wherein the cylinder bore (26) and the first blind bore (42) extend atleast approximately radial to the rotation axis (13) of the drive shaft(12), and wherein the second blind bore (50) extends at leastapproximately parallel to the rotation axis (13) of the drive shaft(12).
 19. The pump according to claim 10, wherein the housing part (10)contains a drive shaft (12) supported so that it can rotate in order todrive the at least one pump element (14), wherein the cylinder bore (26)and the first blind bore (42) extend at least approximately radial tothe rotation axis (13) of the drive shaft (12), and wherein the secondblind bore (50) extends at least approximately parallel to the rotationaxis (13) of the drive shaft (12).
 20. The pump according to claim 12,wherein the housing part (10) contains a drive shaft (12) supported sothat it can rotate in order to drive the at least one pump element (14),wherein the cylinder bore (26) and the first blind bore (42) extend atleast approximately radial to the rotation axis (13) of the drive shaft(12), and wherein the second blind bore (50) extends at leastapproximately parallel to the rotation axis (13) of the drive shaft(12).
 21. The pump according to claim 14, wherein the housing part (10)contains a drive shaft (12) supported so that it can rotate in order todrive the at least one pump element (14), wherein the cylinder bore (26)and the first blind bore (42) extend at least approximately radial tothe rotation axis (13) of the drive shaft (12), and wherein the secondblind bore (50) extends at least approximately parallel to the rotationaxis (13) of the drive shaft (12).
 22. The pump according to claim 8,further comprising, for each pump element (14), a separate housing part(10) containing the cylinder bore (26), the first blind bore (42), thevalve seat (44), and the second blind bore (50) for the pump element(14).
 23. The pump according to claim 9, further comprising, for eachpump element (14), a separate housing part (10) containing the cylinderbore (26), the first blind bore (42), the valve seat (44), and thesecond blind bore (50) for the pump element (14).
 24. The pump accordingto claim 10, further comprising, for each pump element (14), a separatehousing part (10) containing the cylinder bore (26), the first blindbore (42), the valve seat (44), and the second blind bore (50) for thepump element (14).
 25. The pump according to claim 12, furthercomprising, for each pump element (14), a separate housing part (10)containing the cylinder bore (26), the first blind bore (42), the valveseat (44), and the second blind bore (50) for the pump element (14). 26.The pump according to claim 14, further comprising, for each pumpelement (14), a separate housing part (10) containing the cylinder bore(26), the first blind bore (42), the valve seat (44), and the secondblind bore (50) for the pump element (14).
 27. The pump according toclaim 17, further comprising, for each pump element (14), a separatehousing part (10) containing the cylinder bore (26), the first blindbore (42), the valve seat (44), and the second blind bore (50) for thepump element (14).